Hydrocarbons resulting from evaporation in a fuel tank and an intake manifold are recognized as a cause of photochemical smog. Thus, an increasingly tighter regulation is being imposed on a fuel evaporation rate.
For example, a fuel evaporative emission control device disclosed in Japanese Patent Application Laid-open No. 2013-139751 includes: a connecting passage connecting an intake passage of an internal combustion engine and a fuel tank; a canister for adsorbing fuel evaporative gas incoming through the connecting passage; a connecting passage opening/closing unit switchable between open and closed positions to allow and block flow from the connecting passage to the intake passage; a canister opening/closing unit switchable between open and closed positions to allow and block flow between the canister and the connecting passage; a tank opening/closing unit switchable between open and closed positions to allow and block flow from the fuel tank to the connecting passage; and a tank pressure detection unit for detecting internal pressure of the fuel tank. In the fuel evaporative emission control device, in a state where the internal pressure of the fuel tank is equal to or higher than predetermined pressure and the connecting passage opening/closing unit is put to the closed position, the canister opening/closing unit is put to the closed position, so that the canister is closed, and at the same time, the tank opening/closing unit is put to the open position, so that the fuel tank is opened to the connecting passage. Then, the connecting passage opening/closing unit is put to the open position after passage of a predetermined period of time, so that the connecting passage is connected with the intake passage. In the fuel evaporative emission control device, what is known as purging is executed after the internal pressure becomes the same between the fuel tank and the connecting passage due to the high pressure fuel evaporative gas in the fuel tank flowing into the connecting passage.